There is increasing societal sensitivity to environmental issues, including minimization of solvent and impurity levels for the purposes of eliminating health concerns, preserving the integrity of the earth's resources, and the like. In that connection, there have been substantial efforts not only in the public sector, but also the private sector, to institute improved environmental practices. This has included the introduction of voluntary and sometimes mandatory standards by which the environmental friendliness of products and services in the marketplace can be judged (see Green Seal Environmental Leadership Standard for Paint GS-11). Products and services which meet such standards, and the commitment to furnishing same, are often referred to as “green”. Indeed, it is considered very valuable to be qualified to apply the designation “green” (or some equivalent) to products and services in commerce.
One area in which the foregoing has become important is construction and renovation products, and especially aqueous latex paints and other water-borne coatings. There are governmental regulations for mandating the environmental friendliness of such paints and other coatings, but typically non-governmental third-party standards are even more rigorous. Examples of the latter standards are LEED, GREENGARD, GREENGARD Children and Schools, MPI Green Performance, Green Seal, and Collaborative for High Performance Schools. Pursuant to standards such as these, levels of solvents and impurities such as volatile non-aqueous constituents (sometimes referred to in this specification as “VNCs”), alkylphenol ethoxylates (sometimes referred to in this specification as “APES”), crystalline silica, and formaldehyde are controlled.
However, simply minimizing the amount of environmentally undesirable substances in paints and other coatings is recognized to be insufficient. Instead, the “greening” of paints and other coatings would preferably be achieved without undue loss of performance in providing protection for surfaces which they are utilized to cover. For instance, the MPI Green Performance standard “therefore requires that all products shall meet or exceed the performance requirements of the applicable MPI product standard.” The point is that “greening” should, to the extent possible, not entail sacrificing properties which are conventionally taken as characterizing proper paint performance.
Achieving the dual objectives of “greening” paints and other coatings while maintaining good performance is a challenging proposition. We have seen that formulating aqueous latex paints and other water-borne coatings in accordance with “green” principles commonly leads to degradation of at least one important property, and often more than one, in the paint or other coating in question. More specifically, in our experience paint/coating performance can be characterized by: Stormer viscosity stability; rheological profile; flow/leveling and sag resistance; water sensitivity; and color transfer resistance. When an aqueous latex paint or other water-borne coating is “greened” by minimization of solvent, additive or impurity content such as VNCs, APEs or derivatives, crystalline silica and formaldehyde, it is clearly difficult to prevent the diminution of one or more of those properties.
Further complication arises when aqueous latex paints or other water-borne coatings are tinted. The tinting process is often carried out by means of adding one or more colorant compositions at the point of sale to a pre-formulated base composition. This is a popular and advantageous way of marketing tinted paints or other coatings, especially tinted aqueous latex paints. However, unlike pre-formulated aqueous latex paints and other water-borne coatings, colorant compositions are not generally included within the scope of materials governed by “green” standards (at least non-governmental third-party standards). By way of example, see the MPI Green Performance standard relating to VOLATILE ORGANIC COMPOUND (VOC) REQUIREMENTS, wherein it is prescribed that the “calculation of VOC shall exclude water and tinting color added at the point of sale”, as well as the GS-11 standard wherein it is stated “Low- or zero-VOC paints have experienced increased sales, but many shoppers are not aware that VOC levels may increase with the addition of colorants to the base paint.” It follows that addition of colorant compositions which are not conformed to “green” standards can lead to a “back door” introduction of environmentally undesirable solvents, additives and impurities that undercuts any advantage otherwise gained by “greening” the pre-formulated base compositions. Accordingly, it would be a substantial advance if there were provided aqueous latex paints and other water-borne coatings which qualify for the designation “green” but retain their high performance characteristics, and at the threshold a colorant composition capable of yielding such paints and other coatings.